Unit Operation Thermodynamic System
Every unit operation requires a complete set of thermodynamic methods for generating its required properties. In PRO/II, the selection of thermodynamic methods has been simplified by the concept of the method set. Method sets consist of predefined thermodynamic methods for K-values (VLE and LLE), liquid and vapor enthalpies, entropies, vapor fugacities, and densities. Numerous predefined sets are provided. Multiple thermodynamic method sets may be selected for each flowsheet. For example, a default set may be specified for the overall flowsheet and other method sets used for individual units.
Specifying the Thermodynamic Method for a Unit Operation
The Default Thermodynamic Method
By default, each Unit Operation uses the Default Thermodynamic System as defined in the Thermodynamic Data Window.
The Default system used for the thermodynamic calculations within individual unit operations is that selected as Default in the Thermodynamic Data Window.
If the Default system is changed in the Thermodynamic Data Window, unit operations that have the "Default" choice selected for their thermodynamic method calculations will automatically use the new "Default" method.
Individual Thermodynamic Methods
If you have defined more than one thermodynamic system for your flowsheet simulation, you may specify which of the defined thermodynamic systems is to be used for the thermodynamic calculations for a specific unit operation. To change the thermodynamic system used for a specific unit operation, select the desired thermodynamic system from the list of available choices within the desired unit operation.
For unit operations that have a "specific" thermodynamic system selected, changing the Default system in the Thermodynamic Data Window will have not change the thermodynamic method used within that unit operation.
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